When creating something like this, I have to bear in mind the overall composition all of the time. From a distance, the viewer needs to see the overall tone changing gradually from the sunlit side of the Hill to the shaded side. So the details must be drawn/painted not only so that they make sense "locally", but also so that they fit comfortably within the broad sweep of the whole thing. Quite a balancing act, when you're relying on the white of the paper for the highlights, rather than being able to paint them back in - I guess it just comes with experience. Though I do remember having to go back and darken some previously painted parts of this, once I saw the overall tonal range developing. As with a lot (all) of paintings, you need to step back and study the whole composition as it progresses - musn't lose sight of the big picture! With this sort of painting I enjoy depicting things by, well, not painting them! Like the gate here, which isn't painted at all - it's there only because bits of whatever's behind it have been painted in.